Day: July 25, 2012

According to a recent story in Science Daily, new species of sea stars may have arisen in as little a time as 6,000 years.

Researchers studied the diversity in DNA sequences from sea stars of two related species to estimate how long it has been since the two species diverged. Their results showed a range from roughly 6,000 to 22,000 years ago.

That rules out some ways new species could evolve. For example, they clearly did not diverge slowly with genetic changes over a long period of time, but were isolated quickly.

Over the last 11,000 years, the boundary between cold and warm water in the Coral Sea has fluctuated north and south. A small population of the ancestral sea stars, perhaps even one individual, might have colonized a remote area at the southern end of the range then been isolated by one of these changes in ocean currents.

These two species of “cushion stars” – Cryptasperina pentagona and C. hystera – while they look very similar, are very different in many aspects – habitat and sex lives in particular.

Pentagona has male and female individuals that release sperm and eggs into the water where they fertilize, grow into larvae and float around in the plankton for a few months before settling down and developing into adult sea stars.
Hystera are hermaphrodites that brood their young internally and give birth to miniature sea stars ready to grow to adulthood.

Six thousand years is a remarkably short time for a significant evolutionary activity – about the entire length of recorded human history. And about as long as some creationist crackpots think the Earth has been in existence. But it’s not a one-speed-fits-all for evolutionary change. Even the longer 22,000 years is still remarkably short. That’s about when the first Europeans arrived in North America, or the length of the time it takes the remarkable planetoid, 2006 SQ372, to complete its orbit.

Earlier this year, Wired Magazine published a story about research to discover how long it would take for a mouse-sized animal to evolve to an elephant-sized one. And the answer was 24 million years.

That’s how many generations a new study estimates it would take to go from mouse- to elephant-sized while operating on land at the maximum velocity of change. The figure underscores just how special a trait sheer bigness can be.
“Big animals represent the accumulation of evolutionary change, and change takes time,” said evolutionary biologist Alistair Evans of Australia’s Monash University.
Evans and co-authors revisit a fossil record dataset of mammal body size during the last 70 million years, in a study published Jan. 31 in Proceedings of the National Academy of Sciences. The data was originally used to describe the evolutionary growth spurts experienced by mammals soon after dinosaurs ceased to be Earth’s dominant animals.
The relative sizes of mouse and elephant skulls. To go from mouse-sized to elephant-sized would take at least 24 million generations.
For the previous 140 million years, mammals had been rat-sized or smaller. With dinosaurs significantly reduced, mammals had a chance to fill newly vacant ecological niches, particularly that of the large-bodied plant-eater.

But what about human evolution? We have a pretty good record of our species’ evolution over more than 4 million years, from the apelike Ardipithecus through Australopithecus, Neanderthal, Cro Magnon to us. But we are, like other animals, still evolving. And the rate of evolution may be speeding up.

Explosive population growth is driving human evolution to speed up around the world, according to a new study.
The pace of change accelerated about 40,000 years ago and then picked up even more with the advent of agriculture about 10,000 years ago, the study says.
And while humans are evolving quickly around the world, local cultural and environmental factors are shaping evolution differently on different continents.
“We’re evolving away from each other. We’re getting more and more different,” said Henry Harpending, an anthropologist at the University of Utah in Salt Lake City who co-authored the study.
For example, in Europe natural selection has favored genes for pigmentation like light skin, blue eyes, and blond hair. Asians also have genes selected for light skin, but they are different from the European ones.
“Europeans and Asians are both bleached Africans, but the way they got bleached is different in the two areas,” Harpending said.
He and colleagues report the finding this week in the journal Proceedings of the National Academy of Sciences.

And some birds may be evolving faster, too – depending on their colour. According to a story in Science Daily in May,

Researchers have found that bird species with multiple plumage colour forms within in the same population, evolve into new species faster than those with only one colour form, confirming a 60-year-old evolution theory.
The global study used information from birdwatchers and geneticists accumulated over decades and was conducted by University of Melbourne scientists Dr Devi Stuart-Fox and Dr Andrew Hugall (now based at the Melbourne Museum) and is published in the journal Nature.
The link between having more than one colour variation (colour polymorphism) like the iconic red, black or yellow headed Gouldian finches, and the faster evolution of new species was predicted in the 1950s by famous scientists such as Julian Huxley, but this is the first study to confirm the theory.
By confirming a major theory in evolutionary biology, we are able to understand a lot more about the processes that create biodiversity said Dr Devi Stuart-Fox from the University’s Zoology Department.

So much science, so much research that continues to prove Darwin’s original theory, albeit much refined today thanks to our genetic research. You have to wonder, then, why 46% of Americans and 42% of Canadians and many others in the world still believe in the nonsense of creationism nor the pseudoscience of “intelligent” design.

I blame the continued survival of creationism on our failing education system with its lack of emphasis on science and its lack of training in critical thinking; on our society’s growing distrust in and disrespect for intellectuals; and the increasing influence of fundamentalist religion in politics.

Diego’s Quotes

"No humane being, past the thoughtless age of boyhood, will wantonly murder any creature which holds its life by the same tenure that he does. The hare in its extremity cries like a child. I warn you, mothers, that my sympathies do not always make the usual phil-anthropic distinctions."Henry David Thoreau, Walden, Ch. 11: Higher Laws